Tripeptides blood plasma

From potentiometric and spectroscopic studies it is concluded that the main species at neutral pH is a 1 1 tridentate chelate (11) with a log stability constant of ca. — 4. The claim55 that the stability of this species is comparable to that of the Cu(albumin) complex is rather surprising, since for this to occur the involvement of a histidine in the third amino add position is normally required, and furthermore others have concluded that in blood plasma at least the tripeptide is unlikely to compete against other ligands for the available Cu11.56,57 To illustrate the point that such conclusions from blood plasma simulations are only applicable to that medium, Pickart and Thaler58 have shown that in a cell culture medium the tripeptide considerably enhanced Cu uptake into cells and that this was not affected by a 300-fold molar excess of amino adds, including histidine. 

Trimethylenediamine, N-(2-aminoethyl)-metal complexes, 49 Tripeptides metal complexes blood plasma, 966... 

Glutathione, a tripeptide, primarily exists in the form of GSH (L-y-Glu-L-Cys-Gly, MW 307 Fig. 1) and is the major low-molecular-weight thiol compound in animals and plants. GSH is present in millimolar concentration in mammalian cells (1) the highest concentrations are found in the red blood cells, liver, pancreas, kidneys, spleen, eyes, lungs, and intestinal cells. The plasma concentration of GSH is 0.004 to 0.006 mM. 

Protein degradation continues in the lumen of the intestine. The pan creas secretes a variety of proteolytic enzymes into the intestinal lumen as inactive zymogens that are then converted into active enzymes (Sections 9.1 and 10.4). The battery of enzymes displays a wide array of specificity, and so the substrates are degraded into free amino acids as well as di- and tripeptides. Digestion is further enhanced by proteolytic enzymes, such as aminopeptidase N, that are located in the plasma membrane of the intestinal cells. Aminopeptidases digest proteins from the amino-terminal end. Single amino acids, as well as di- and tripeptides, are transported into the intestinal cells from the lumen and subsequently released into the blood for absorption by other tissues (Figure 23.1). 

Nerve agents also react with a tyrosine residue associated with the albumin fraction in blood (Black et al, 1999) (Figure 10). Analysis of tryptic digests from plasma incubated with sarin identified a phosphylated tripeptide, MeP(0)(0 Pr)-Tyr-Thr-Lys, consistent with the protein being albumin (tyrosine residue 411), although this sequence is common and occurs in other proteins. Before the advent of modern mass spectrometry, diisopropyl fluorophosphate was reported to... 

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